Adaptive minimum variance beamforming combined with phase coherence imaging for ultrasound imaging

Abstract

Delay-and-sum (DAS) beamformer is extensively used in ultrasound imaging. However, the DAS beamformed signals have wide main lobe widths and high side lobe levels, which result in images with limited resolution and low contrast. Recently, a new signal processing method named phase coherence imaging (PCI) for side and grating lobes suppression was proposed. It was based on a statistical analysis of the phase dispersion in the received signals. The contrast could be significantly enhanced. For spatial resolution improvement, adaptive minimum variance (MV)-based beamformer presented in the ultrasound imaging literatures shows great potentials by minimizing off-axis signals, while keeping on-axis ones. In this paper, MV beamforming combined with PCI is introduced to effectively increase the imaging resolution and contrast simultaneously and outperform both MV and PCI beamformers. Two phase coherence factors, the phase coherence factor (PCF) and the sign coherence factor (SCF), are computed based on the measurement of the phase diversity of the received aperture data, and then used to weight the MV beamformed channel sum output. Simulations with point and cyst phantoms using FIELD II demonstrate the expected performance of the proposed beamforming method.